The tie that binds all five of these sophomores is that they each rushed for at least 600 yards as a rookie (Ball was at 559 yards). With that 600-yard baseline in mind, I looked back at how running backs over the last decade have fared in this situation. The top line on each entry is the second-year numbers. The bottom line, in parentheses, is the rookie-year numbers :

The tie that binds all five of these sophomores is that they each rushed for at least 600 yards as a rookie (Ball was at 559 yards). With that 600-yard baseline in mind, I looked back at how running backs over the last decade have fared in this situation. The top line on each entry is the second-year numbers. The bottom line, in parentheses, is the rookie-year numbers :

Keep reading for takeaways, notes on this year's sophomore backs and conclusions.

TREND TAKEAWAYS 1) Between 2003 and 2012, 33 rookie running backs have rushed for 600 or more yards. 22 of them have suffered a decline in yardage as sophomores.

2) Between 2003 and 2012, 12 rookie running backs have rushed for 1000 or more yards. Nine of them have suffered a decline in yardage as sophomores. The only three that didn’t were Domanick Williams, Adrian Peterson and Chris Johnson.

BUT WHY? To be honest, I really don’t know why runners that had success as rookies to fail so often as sophomores. I didn’t expect it. When I think of career arcs, I typically think of a sharp rise from Years 1 to 2 and then gradual improvement from there until the peak.

Overuse was not usually an issue. Just eight of these 33 backs had 250+ carries as rookies. Serious injuries were not a huge factor either as only seven guys (Mike Bell, Selvin Young, Steve Slaton, Beanie Wells, Roy Helu, Vick Ballard, Doug Martin) missed significant time. Many of these guys – Slaton, Wells, Martin particularly as really high fantasy picks – were really bad even before their injury.

CONCLUSIONS This evidence isn’t meant to be taken as a be all, end all in terms of discussion on second-year running backs. Each player should be evaluated individually, with trends like this as one piece of the puzzle. Take the facts stated here and put as much emphasis on them as you wish.

As noted at the of the “But Why?” section, a big part of the whole evaluation should be raw talent. Eddie Lacy oozes it, and he’s trending up with Aaron Rodgers (collarbone) fully healthy. … My bigger concerns are in Zac Stacy and Le’Veon Bell because they fell into category 4. Stacy does get a boost with Sam Bradford (neck) expected back. … The numbers in category 5 prove that simply blowing the doors off defenses as a rookie doesn’t mean a player will continue to do so in Year 2. Andre Ellington prospectors should take note – even with the addition of free agent LT Jared Veldheer and return of stud LG Jonathan Cooper (leg). … I still absolutely love Giovani Bernard because I think his situation has changed. Run-first Hue Jackson’s promotion to offensive coordinator is monstrous.

I remain really high and Lacy and Bernard. I think the ADPs of Stacy, Bell and Ellington will end up too rich for my blood, especially after digesting the above data.

Adam Levitan is in his sixth season covering football and basketball for Rotoworld. He won the Fantasy Sports Writers Association award for Best Series in 2011 and 2009, and ESPN's overall fantasy football title in 2000. Find him on Twitter.Email :Adam Levitan